1. Field of the Invention
The present invention relates to a semiconductor device having a semiconductor nonvolatile memory element, specifically, relates to a method for manufacturing of a semiconductor device including a floating gate electrode formed with semiconductor particles.
2. Description of the Related Art
EEPROM (Electrically Erasable and Programmable Read Only Memory) and a flash memory are know n as a memory representing a semiconductor nonvolatile memory. As for the nonvolatile memory, a conductive layer serving as a charge accumulating layer or a floating gate type memory including a polysilicon layer is representative.
With recent reduction of devices in size, thinning of a tunnel oxide film of a semiconductor nonvolatile memory has been conducted. In the current situation, there is caused a defect such as a deterioration of the tunnel oxide film caused in forming films or a set of operation such as writing or erasing data (operation of injecting, holding, emitting charges, or the like). In a conventional floating gate type memory element, if a defect is caused even in one part of the tunnel oxide film, electric charges accumulated in the floating gate electrode are leaked through the defect that has become a pass, and thus the memory element cannot operate as a memory.
Reference 1 (Japanese Patent Laid-Open No. H11-87544) describes that a silicon quantum structure (hereinafter, referred to as a silicon dot) is used as a floating gate electrode instead of a conductive layer or a polysilicon layer. Here, the silicon dot is formed by a LPCVD (low pressure chemical vapor deposition).